1. Field of the Invention
The present invention relates apparatus for absorbing sound waves radiated from an air cooled engine and its cooling fan, and particularly to the use of such an apparatus with a lawn and garden vehicle.
2. Description of the Prior Art
Various laws and regulations make it desirable to restrict the level of lawn and garden vehicle sound to which the operator is exposed.
While compliance can and often is easily met by providing the operator of such vehicles with ear plugs and/or sound blocking personal protection devices, that type of compliance may not be practical in some circumstances. For example, sound blocking devices often block out the sounds of other vehicles, people and/or traffic which may be near the operator and of which he should be aware for his own and their safety. Further, the use of such protection makes it difficult for the operator to monitor the performance of the engine, belts, and other accessories as indicated by their respective sounds.
Sounds which radiate from engines and which must be controlled include the engine and its operating components, such as bearings, pistons, valves, rods, etc. On air cooled engines, significant volumes of air are required to maintain the desired engine operating temperature. To provide this air are cooling fans which generate substantial levels of sound.
Various structures have been utilized to absorb these various sounds before they reach an operator. For example, on the John Deere Model 185 air cooled lawn and garden tractor, the hood encloses the upper portions and top of the engine and serves to deflect and deaden the sounds radiating from the engine and its components. An optional feature provides for sound absorbing material to be attached to the inside of the hood enclosure to further absorb the sounds.
Since the Model 185 vehicle draws its cooling air from intake openings positioned near the bottom of the hood enclosure, the sounds radiating through those openings are sufficiently removed from the operator's ears to reduce the contribution of those sound sources to the total sound level encountered by the operator. Accordingly, the enclosed hood structure and foam has proven satisfactory for limiting the sound levels encountered by operators of the Model 185 air cooled vehicle with its air intake arrangement.
The lawn and garden tractor design of the prevent invention positions the engine air intake at the top of the hood enclosure and close to the operator. This design provides cleaner air for the engine since that air comes from a higher level than air which is drawn into the bottom levels of a hood enclosure and which could be contaminated with grass clippings and similar materials. This air is also cooler since it need not be drawn around the engine and to the fan as is the case with the air drawn into the lower hood openings. While improving the engine cooling, this design allows the engine, component and fan sounds to travel directly out through the air intake opening and to the operator. Accordingly, the decibel levels experienced by the operator can be higher than desired.
To reduce such sound levels in this design and yet permit sufficient cooling air to be made available to the air cooled engine, there is provided in the air intake opening an improved sound wave absorbing apparatus which also permits sufficient air flow to the engine cooling fan.